This invention relates to improvements in a known unit for coupling a displaceable operating member such as a bar or shaft with at least one regulating member, in particular a regulating rod, of a fuel injection aggregate of an internal combustion engine, which unit comprises
a unit casing having a bore,
a cam adapted for being firmly clamped, by screw means such as a screw bolt, on the operating member to project transversely therefrom, and engaging the regulating member,
abutting means such as a stop or the like for limiting the movement of the regulating member in one direction,
which cam is provided with nut means having an internal threading for engaging the screw means,
the operating member having a first transverse bore being associable with a bore of the said unit casing, and
a preferably cylindrical fixing and positioning pin which is adapted for being set, during an initial step of the assembly of the regulating member or members with the operating member, in the last-mentioned unit casing bore as well as in the first transverse bore of the operating member and secures the said operating member against displacement of any kind relative to the casing.
It is essential in such regulating units to achieve an exact initial positioning of the members. Therefore, during assembly, the regulating member must be urged against the abutment means, and the cam must be clamped firmly on the operating bar or shaft in a position such that no play is left between the operating member and the regulating member, and that, moreover, the cam will retain its position, fixed by clamping in the abutting state, in relation to the operating member, as otherwise inaccuracies will occur when the regulating member is subsequently adjusted.
In structures we know to exist in industry the cam comprises a hub having a piercing elongated slot, by means of which hub it is mounted on the operating bar or shaft. By means of the above-mentioned screw the elongated slot is narrowed, thus resulting in a clamping of the cam on the operating member. However, as it is necessary for the hub to possess a certain radial play on the operating bar or shaft, there results a certain tilting of the hub axis vis-a-vis the axis of the operating member when the cam is pressed against the regulating member being in abutting position. During subsequent firm clamping, there results a distorting force which causes a certain springing back or repelling movement of the operating bar or shaft when the respective regulating member is released from its abutting position.
Thereby the initially achieved fine adjustment will not be preserved notwithstanding an effective clamping of the cam on the regulating rod. This drawback becomes particularly important when the operating member bears several cams for the simultaneous adjustment of several regulating members, such as is the case in internal combustion engines having several cylinders and fuel injection aggregates being each individually associated with a different cylinder, respectively, which injection aggregates comprise each a regulating rod, and all of these regulating rods must be shifted simultaneously in operation.
In a unit of the initially described kind disclosed in the European Offenlegungsschrift No. 55 245, the operating bar has an angular profile on which angular cams are mounted. Screws are inserted through holes in the operating bar which clamp the cams fast on the bar by means of nuts. Due to the play of the screw bolts in the holes, and between the cams and the operating bar, it is not possible to attain in this case an exact permanent clamping of the cams on the operating bar relative to the initial or basic position of the parts. Moreover the angular profile of the operating bar gives rise to problems with regard to its support in the unit casing, as the necessary bearings are difficult to manufacture.